Pboduction of abrasive floubs



.S. F. WALTON Sept. 6,

- PRODUCTION OF ABRASI'VE FLOURS Filed March I, 1950 f V i T A U Inventor Jana/61370511012 7 5 Z mornigy Patented Sept. 1932 UNITED I STATES PATENT OFFICE.

SAIUHJI. WALTON, more, NEW YORK, ASSIGN OB TO THE EXOLON GOHPANY, OI BLASDELL, m YORK, A CORPORATION OF MASSACHUSETTS mnncrron or masrvn nouns Application fled larch 1, 1830. Serial No. 488,328.

to to the trade.

ere treated chemically, long and involved rocesses were necessary, with further di culties of washing the flours free from the chemicals used. Even after such washing, however, there still remained extremely fine deleterious matter, such as' graphite, in the flour, and moreover this long washing resulted in the loss of valuable :0- fines.

Where treated mechanically, as by means of pebble mills, the grains were reduced by a long and tedious attrition process to flours of fair quality, provided that the quality of :5 ,the original crude material was exceptionally free from contamination or impurities. These pebble mill flours for certain uses how ever required subsequent chemical treatment, and such chemical treatment represents a second long and involved process following the actual milling itself.

My present invention contemplates the production of such flours free from contamination, by methods and apparatus which are at once simple and inexpensive so as to lend themselves to commerclal'practice and by means of which the time and cost factors of the methods of treatment heretofore emloyed may be reduced to the minimum.

40 y invention also contemplates a resultant product which is characterized by a freedom from impurities and contaminations never heretofore attained the art.

In racticing my invention I break down the a rasive grains by the air blast method disclosed in the Harty-Moore application entitled Art of processing abrasive grains or the like. Under such method, a certain amount of the abrasive material broken down b the air blast impaction is carried ofi'by air draft, the coarser material in such air' stream fallingoutby gravity, and ac cording to'my method, being recovered and impacted agaln and again until the material is all as fine as desired or only a small percentage remains to be reduced.

As illustrative of the principles involved, I shall discuss my invention in its ada tation to the production of silicon car ide flours. It will be understood, however, that this treatment is purely illustrative and in no way limitin and that the principles apply to the pro'uction of any kind of flour wherein the flour is an item of recovery, so to speak, based upon the initial reduction of a heavier particle and during such reduction, the release of lighter particles which ultimately are converted into flour. According to my invention, considering the abrasive grain as illustrative, I first crush in any' suitable manner, as by rolls, crude abrasive silicon carbide to a size wherein it will all pass, say an eightmesh screen. This material is then given a preliminary air-blasted impaction wherein any flours produced are usually too impure to be retained. Following this, the remaining material is repeatedly broken down by air blast im actions and the resultant flours carried o by draft. These flours are separated out of the air stream by any means such as an air gallery or cyclone separators, the extremely ,fine material unsatisfactory for use because of extreme fineness and contamination, etc., being collected in an suitable dust arrestor.

To accomplish this finer breakdown and separation, and particularly to prevent during such breakdown and separation the incorporation of unwanted coarse material, I use the equipment disclosed diagrammatically in the accompanying drawing, which Fig. 1 is a diagrammatic view of one form 'of equipment for the practice of my invention, and

Fig. 2 is-a similar view showing a modification.

In accordance with m and following the metho dlsclosed in said Harty-Moore application, the abrasive grains after preliminary crushing as by rolls to six and eight mesh or finer, are pro'ected as a grain stream of redetermine ve ocity into a reducing cham er having a grain impingement surface therein. For the pur oses of this application, the reducing cham er is indicated at 1, the air blast'nozzle at 2,- and the impingement surface at 3. Preferably, though not necessarily, the im ingement surface 3 is a block of material 'ke the thereagainst from t e nozzle 2 and as a recess 4 alined with saidnozzle and either pro-formed therein or worn therein by the attritive action of the grains discharged thereagainst.

In the form shown in Fig. 1 an angularly disposed screen above the block 3 retains the unwanted coarse sizes for re-impaction, such coarser sizes dischar g by gravity as at 5 into any suitable co ection receptacle. The fine abrasive'grains which, however, still are coarser than the wanted flours pass general concept through screen 4 into a collecting chamber 6, whlch is bafiied as at 7 to shunt the path of the fines into a cyclone separator 8, the

exit 9 of which leads to a second cyclone or to a dust arrestor. The heavier particles in chamber 6 discharge by gravity as at 10 into any suitable collection receptacle, and the same is true as regards the separator 8, the gravity discharge for which is indicated at 11.

The successively finer particles, which,

however, are not yet. of the desired degree of fineness, discharging from the respective avity outlets 5, 10 and 11, are again introdined through air-blast nozzle 2 into the reducing chamber and subjected to further reduction and this procedure is repeated again and again until the grains are all as fine as desired. With each successive repetis tion of the rocedure, a certain percentage of extremely e material is separated out of the air stream by the cyclone or other separator 8, these representing material which is of such extreme fineness and so contaminat-' ed as to be wholly undesirable, and which is simply collected in the dust arrestor.

In the modification of Fig. 2, .12 is the chamber in which the breakdown occurs, 13 and 14 are staggered baflies which prevent unwanted coarse sizes being-carried over into the chamber 16,and ,17 is a baflie inserted in chamber 16 to obstruct the air stream and shunt the fines into the air galains being pro'ected.

s irit and sec lery or the cyclone se arator 18, from which the unwanted fines discharge into any suitable dust arrestor, as in Fig. 1.

It is obvious that other adaptions would accomplish a similar separation of wanted flours from unwanted coarse grain.

The flours produced by my process are exceptionally clean, free from extraneous mat-- tory without further treatment for most purl poses, if flours of exceptional purity are desired, a li ht chemical treatment is found to give satis actory results. The washing and drying and elutriating of these flours invo ves no particular problem.

As suggested, the drawing and description are to be understood as su gestive rather than inclusive, as it is obviousfy impractical within the limits of this specification to catalo or enumerate all the various materials an procedures which might be involved in the practice of the concepts involved.

All variations in method and ap aratus, however, are to be regarded as maiin the of our invention, ifwithin t e limits of t e appended claims.

What I therefore claim and desire to secure b Letters Patent is:

1. apparatus for producing abrasive flours, in combination, an air blast for projecting a grain steam, a reduction chamber into which said stream is delivered, an impingement surface within said chamber and so located with reference to said air blast that a recess is worn in said surface by attritive action of the grains projected thereagainst whereby the grains have a colliding action with each other and a caroming action off the walls of the recess efi'ective both to reduce them-to the desired size and simultaneously impart to them a permanent capillarity, and a collection chamber commumcating with said reduction chamber, said chambers having a common outlet for the lighter products of reduction and said reduction chamber having a baflled outlet into said collection chamthereinto through said baflled outlet of the reduction chamber and dropping out of the air stream into said collection chamber whereby said lighter products may be collected.

2. Apparatus'as claimed in claim 1 wherein the impingement surface is 'of a material which is substantially as hard as the grains being reduced.

In testimony whereof I afiix m signature. SAMUEL F. ALTON. 

